docs: def process_file(params):
      """
      Processes a file and returns the parsed MRZ (or None if no candidate regions were even found).
  
      The input argument is a list (filename, save_roi, extra_params).
      (Because we need to use this function within imap_unordered)
      """
      tic = time.time()
      filename, save_roi, extra_params = params
      result = read_mrz(filename, save_roi=save_roi, extra_cmdline_params=extra_params)
      walltime = time.time() - tic
      return (filename, result, walltime)